Some people write something like ****TRIGGER**** or other warning notes before they reveal what they consider their spoiler. Since triggers are personal, I don't know that any additional warnings would be very useful since one would have to know the subject/material that was being hidden to know if it was going to trigger one and that would be too late? Triggers really only say what is triggering to the person posting the warning. I don't think there are any "generic" triggers.